Investigation of the properties of decaoxyethylene n‐dodecyl ether, C12E10, in the aqueous sugar‐rich region

Abstract

AbstractInterfacial, thermodynamic, and morphological properties of decaoxyethylene n‐dodecylether [CH3 (CH2)11(OCH2CH2)10OH](C12E10) in aqueous solution were analyzed by tensiometric, viscometric, proton nuclear magnetic resonance (NMR), and small‐angle neutron scattering (SANS) techniques. Dynamic and structural aspects at different temperatures in the absence and presence of sugars at different concentrations were measured. Critical micelle concentrations (CMC) were determined by surface tension measurements in the presence of ribose, glucose, and sucrose. The heat capacity (ΔCp.m.), transfer enthalpy (ΔHm.tr.), transfer heat capacities (ΔCp.m.tr.), micellization constant (Km), Setchenow constant (KSN), and partition coefficient (q) were determined and discussed as an extension of the usual thermodynamic quantities of micellization and adsorption at the air‐water interface. An enthalpy‐entropy compensation effect was observed with an isostructural temperature (Tc) of about 310 K for both micellization and interfacial adsorption. SANS measurements were taken to elucidate structural information, viz., aggregation number (Nagg), shape, size, and number density (Nm) on C12E10 micelles in D2O at different concentrations of sugars (0.05, 0.02, 0.3, and 0.5 M) and temperatures (30, 45, and 60°C). Intrinsic viscosity gave the hydrated micellar volume (Vh), volume of the hydrocarbon core (Vc), and volume of the palisade layer of the oxyethylene (OE) unit (VOE). SANS, as well as rheological data, supported the formation of nonspherical micelles with or without sugars. By SANS, we also observed that at the studied temperature intervals, oblate ellipsoid micelles changed into prolate ellipsoids and the number density of micelles decreased with an increase in temperature both in the presence and in the absence of sugars and also on increasing the concentration of sugars. Proton NMR showed a change in chemical shift of the OE group of micelles above the CMC. We also studied the phase separation of C12E10 by sugars in cloud point measurements.